Acoustic device



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E. D. cocj'rs ACOUSTIC DEVICE Filed March a, 1955 July 27, 1937.

Patented July 27, 1937 assist ACOUS'EEC DEVECE E. Donald Coots, Chicago, llL, assignor, by niesne assignments, to Reconstruction Finance Corporation, (lineage, lit, a corporation Application March 6, 1935, Serial No. 9,641

13 Glaims.

My invention relates to acoustics. and has more particular reference to sound reproducing apparatus particularly adapted for the faithful reproduction of every sound component Without distortion or modification.

An important object of the present invention is to provide a sound reproducer capable of transmitting a substantially exact reproduction of each sound component within the frequency range of audible sound vibrations.

Another important object is to provide a sound reproducer adapted to faithfully reproduce the true pitch of the original vibration with equal accuracy at high as well as low sound frequency so that substantially every component of the sound being reproduced will be transmitted by the reproducer.

Another important object is to provide a sound reproducer comprising a cabinet having a portion adapted to vibrate at different frequencies in order to accurately reproduce all of the components of the sound wave.

Another important object is to provide a sound reproducing baffle having graduated portions each adapted to vibrate at different frequencies for the purpose mentioned.

Another important object is to provide a sound reproducing bafiie having interconnected portions adapted to vibrate at different frequencies Whereby the baffle, in its entirety, comprises a reproducing element adapted to vibrate at substantially every frequency within the range of the sound produced, to the end that a substantially true sound reproduction may be accomplished.

Another important object is to provide a sound reproducing bafiie of graduated thickness to the end that the baiiie may vibrate at various periodic frequencies Within its area in order to accomplish a substantially faithful reproduction of sound.

Another important object is to provide a sound reproducing baffle having concentric zones of increasing thickness throughout the area of the bafile.

Another important object is to provide a sound reproducing baiiie comprising a laminated element of varying thickness throughout the area of the baffle.

Another import-ant object is to provide a sound reproducing baffle of minimum thickness in its central portions and increasing in thickness progressively toward the marginal portions of the baffle.

Another important object is to provide a sound reproducing bafile having a central perforation and portions of minimum thickness defining said (Cl. Isl-31) perforation, the baffle increasing in thickness progressively toward its marginal portions and a mechanical sound reproducer operatively connected with the portions of minimum thickness in order to vibrate said baffle.

Another important object is to provide a sound reproducer comprising a cabinet including a vibratable sound reproducing portion of the character mentioned.

Another important object is to provide a sound reproducer comprising a cabinet having a sound source positioned to project sound waves in a predetermined direction and means formed in said cabinet for deflecting the sound waves in a plurality of directions in order to scatter the reproduced sound.

Another important object is to provide a sound reproducer including means to project sound Waves in a predetermined direction and substantially Wedge-shaped vanes positioned in the path of the projected waves to deflect the same laterally in order to scatter or diffuse the sound waves throughout substantially the entire area in front of the Wave projecting means.

Another important object is to provide a sound reproducer including means to project sound Waves in a predetermined direction and deflectors positioned in the path of the projected waves to cause at least a portion of each wave to be diffused laterally in a plurality of directions While 3 the remainder of each Wave may travel unobstructedly in the direction of its projection to the end that the intensity of the reproduced sound may be substantially uniform throughout a wide area in front of the wave-projecting means.

Among the other important objects of the invention are to provide a reproducer capable of developing overtones, harmonics, and other modulations present in sound waves in addition to faithfully reproducing substantially all of the sound components throughout the entire frequency range of audible sound; to provide a reprcducer comprising an attractive cabinet more particularly adapted for housing a radio set although obviously adapted for phonographic and other acoustical purposes, the cabinet having the improved means heretofore mentioned for faithful sound reproduction; and finally to provide the manifest improvement in sounding devices resulting from the accurate reproduction of overtones and modulations as well as all components throughout the entire frequency range of audible sound.

Numerous other objects, advantages, and inherent functions of the invention will be apparent from the following description, which, taken in connection with the accompanying drawing, discloses a selected embodiment of the invention.

Referring to the drawing:

Figure 1 is a perspective view of a sound reproducer embodying my present invention;

Figure 2 is a sectional view taken substantially along the line 22 in Figure 1;

Figure 3 is a sectional view taken substantially along the line 3-3 in Figure 2;

Figure 4 is a sectional view taken substantially along the line 4-4 in Figure 2, the view comprising a plan of a sound reproducing baffle embodying my present invention; and

Figure 5 is an enlarged sectional View taken substantially along the line 55 in Figure 4 in order to better illustrate the form and construction of the sound reproducing element,

To illustrate my invention, I have shown on the drawing a radio receiving set and sound reproducer, although it will be apparent, of course, that the invention is not necessarily restricted to the particular sounding device but may be applied in any acoustical device.

The apparatus shown, however, comprises a cabinet II containing a radio receiving set I3, a sound reproducer I5, and sound diffusing means II arranged in the cabinet.

The cabinet comprises a top wall I9, opposite side walls 2 I, a bottom wall 23, and a supporting base 25. The cabinet also has a front wall Z'I extending downwardly at the forward edge of the top wall I9 toward the bottom wall, the lower edge of the front wall 21 being spaced a substantial distance from the bottom wall to leave an opening. Pedestals 29 are or may be provided or other decorative structural elements arranged between the lower edge of the front wall and the bottom wall 23. The opposed side walls are cut away as at 3I to provide lateral openings extending rearwardly of the forward corners of the cabinet. Within the cabinet a shelf 33 is preferably provided in position extending rearwardly of the lower edge of the front wall and the radio receiver I3 is supported on said shelf in position with its controls 35 and an indicating dial 31 exposed on the front wall 21.

The sounding device I5 comprises a panel or baffle 39 mounted in and forming a part of the cabinet and adapted to be vibrated differentially in various places within its area. The sounding device also includes means preferably comprising a mechanically operating unit II for vibrating the baffle 39 in accordance with the sound to be produced thereby. The unit 4I may comprise any suitable, preferably electrically operated vibrator capable of the mechanical production of sound vibration and the unit is connected with the radio apparatus I3 as by means of the cable 63.

The baffle 39 is mounted in the cabinet in position to project sound vibrations outwardly of the cabinet and is preferably positioned between the shelf 33 and the bottom of the cabinet opposite the forward edges of the cabinet defined by the cut-out portions 3| of the side walls. The baffle comprises a plate-like element of graduated thickness, the element being preferably of maximum thickness in its peripheral portions and having decreasing thickness inwardly toward its portions of minimum thickness in the central portions of the element. The element, for convenience, is preferably of rectangular peripheral configuration having circularly cut corners as shown at 45, although, of course, any preferred configuration may be adopted. The baffle is secured at its edges to a preferably rectangular frame 41 in any suitable or convenient fashion as by means of the bolts 49 and the frame 4f is fastened in the cabinet likewise in any suitable or convenient manner.

The baffle 39, itself, may be formed of any suitable resilient material, although I prefer to utilize wood in its construction. The baffle also may be formed so that its thickness varies continuously between its portions of maximum and minimum preferably as concentric rings, in a surface of L the piece. For the sake of uniformity of the product, however, it is preferable to form the baffle as a laminated element containing layers as shown, the layers being arranged so that the grain of the wood in each layer intersects the 141 grain of the adjacent layers. It is desirable also to utilize wood of as uniform texture as possible in order to obtain uniformity in the final product.

The baffle may be formed by cutting preferably circular openings in the laminae before assem- 1 bling the same, the openings in the several laminae being of different diameters; but I prefer, in making the bafile, to first form a laminated plate in which the layers are imperforate and then cutting away the laminae in order to provide the stepped baffle as shown in Figure 5. The laminae may be secured together in any pre ferred manner as by applying a suitable cement herebetween and squeezing the parts together until the cement has set. It is not, of course, essential to form circular openings in the laminae but the circular configuration is preferred since it facilitates the fabrication of the element. It will be noted also that the panel has a central perforation 5i and that the vlbratable device M is mounted on the panel opposite said perforation, the device having marginal flanges 53 secured preferably as by the fasteners 55 to the thinnest portion of the panel.

When a panel of this character is vibrated in accordance with a composite sound vibration including a variety of frequencies, overtone modulations, and other complex sound components, I find that each component will be transmitted by the baffle in substantially unchanged condition so that the resulting sound produced is a true reproduction of the original vibration impressed upon the radio apparatus or other prime mover, which may be used to activate the bafile. A notable defect in sound reproducing apparatus heretofore provided has been the inability to faithfully reproduce all of the complex components contained in the original vibration so that reproduction is defective either in the omission of high-frequency components, in which case the low tones are unduly emphasized, or in the o1nission of low frequencies, in which case the high pitches predominate and the resulting sound is thin, lacks body, and provides an unreal tinny effect.

My present invention, however, provides not only for the faithful reproduction of both high and low frequency components but also, to an unusual degree, provides for the inclusion of modulations producing overtones controlling the pitch, timbre, quality or character of the sound, so that the resulting reproduction is faithful in every respect through the inclusion of these characterizing modulations.

It will be seen from an inspection of the drawing that the sound reproducing bafiie is mounted. in and forms a part of the cabinet itself and further that the baffle is positioned to project sound waves forwardly of the enclosing cabinet. I prefer to position sound diffusing means ll, which also may form a part of the cabinet structure, in the path of the sound waves advancing from the baflie in order to deflect a part of the sound waves laterally of the cabinet while permitting other portions of the waves to advance forwardly to the end that the entire region in front of the cabinet may receive the transmitted sound at substantially the same intensity in order to avoid a localized loud spot directlyin front of the cabinet.

The sound deflecting means I! comprise a plurality of prismatic members 57 vertically arranged in the cabinet in front of the baffle, the prismatic members being of triangular cross-sectional configuration with the apices of the members facing toward the sound source so that the inclined sides thereof may deflect sound waves impinging thereon laterally. The members 51, however, are spaced apart so that a portion of each sound wave emitted from the source behind the members 57 may travel unobstructedly between the deflecting members. The members 57 may be conveniently in the cabinet in position extending between the lower edge of the front wall 27 and the bottom wall 23, the members being positioned between the corner posts 29.

In order to finish the cabinet attractively, I may provide and arrange a decorative fabric strip 59 in position to overlie the members 51. This fabric may at its central portion pass in front of the members and be connected at its opposite ends on the frame 4? by means of a clamping strut 6| held on the frame by fasteners 53 whereby to clamp the edges of the fabric by and between the frame and the clamping strut 65. Since it is more convenient to apply the decorative fabric in the cabinet prior to the mounting of the baffle 39, the members 49, which secure the bafiie on the frame 41, may also penetrate the clamping strip 5! as shown in Figure 5 so that the baffle frame and clamping strip are secured together as indicated. The decorative fabric 59 preferably extends between the shelf 33. and the bottom wall of the cabinet in order to conceal the baiile as well as the sound deflecting members. Naturally, it is not essential to employ sound deflecting members in conjunction with the baffle nor is it necessary to employ a bailie of the specific form shown herein in conjunction with the sound deflectors. On the contrary, sound deflectors may be used in conjunction with any sound source in order to disperse the waves and eliminate localized loud spots.

It is thought that the invention and numerous of its attendant advantages will be understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction, and arrangement of the various parts, without departing from the spirit or scope of my invention and without sacrificing any of its attendant advantages, the form herein described being merely for the purpose of illustrating the invention, and I do not desire to limit the invention in any way to the particular construction shown.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is as follows:

1. A sound reproducer comprising a wooden baffle board of laminated construction and having a portion in which only one of the laminations extends and adjacent portions containing a plurality of laminae.

2. A sound reproducer comprising a wooden baffle board of progressively varying thickness from the marginal border of the board toward its central portions.

3. A sound reproducer comprising a wooden bafiie board of laminated construction and of progressively varying thickness from the marginal border of the board toward its central portions.

4. A sound reproducer comprising a wooden bailie board of laminated construction and of progressively varying thickness from the marginal border of the board toward its central portions, the marginal portions of the board containing a maximum number of laminations.

5. A sound reproducer comprising a wooden baflie board of laminated construction and or progressively varying thickness from the marginal border of the board toward its central portions, the central portion of said board having minimum laminated thickness.

6. A sound reproducer comprising a wooden bafile board of laminated construction having a central portion of minimum laminated thickness, and adjacent portions outwardly of said central portion of progressively increasing laminated thickness toward the margin of the board.

7. A sound reproducer comprising a wooden baiile board of laminated construction and of progressively varying thickness from the marginal border of the board toward its central portions, all the laminations of the board extending in the marginal portions thereof.

8. A sound reproducer comprising a wooden bafiie board built up of laminations, said laminations having central openings and the opening of each lamination in the structure being different in size from the opening of an adjacent lamination, the thickness of said laminations having an inverse ratio with respect to the size of the openings therein.

9. A sound reproducer comprising a wooden bafile board built up of laminations, said laminations having central openings and the opening of each lamination in the structure being different in size from the opening of an adjacent lamination, the thickness of each lamination being less than that of an adjacent lamination having a smaller opening.

10. A sound reproducer comprising a wooden baffle board built up of laminations, said laminations having central openings and the opening of each lamination in the structure being different in size from the opening in an adjacent lamination, the grain of the wood comp-rising each lamination intersecting the grain of wood in the next adjacent lamination.

11. A sound reproducer comprising a cabinet having a wooden wall built up of laminations, certain of said laminations having central openings and the opening of each lamination in the wall being different in size from the opening of an adjacent lamination whereby said wall has progessively increasing thickness outwardly of the central portions thereof, and means to vibrate said wall.

12. A sound reproducer comprising a cabinet having a wooden wall of laminated construction, said wall having a portion of minimum laminated thickness and adjacent portions progressively comprising additional laminae whereby the wall progressively increases in thickness from a zone of minimum thickness toward a zone of maximum thickness.

13. A sound reproducer comprising a wooden Wall of laminated construction, said wall having an area of maximum thickness comprising a plurality of laminae, and said wall radially decreasing in thickness toward an area of minimum thickness, the Wall portions intermediate the zones of maximum and minimum thickness being concentrically arranged in said Wall.

E. DONALD COOTS. 

